JPH0340886A - Method and apparatus for producing chemical pulp with high sulfidity, using continuous digester - Google Patents

Abstract

PURPOSE: To readily obtain the subject pulp capable of more increasing quality of chemical pulp by circulating black liquor into a steamed crushed cellulose fibrous material to be a part of slurried solution. CONSTITUTION: In a continuous cooking process of high sulfidity paper pulp including steaming a crushed cellulosic fibrous material, slurrying the material with a solution, supplying the steamed material into a cooking tank of the slurry solution, kraft cooking the material in the cooking tank with white liquor, and separating out black liquor from the cooking tank, the black liquor is circulated into the steamed crushed cellulosic fibrous material to be at least a part of the slurried solution, a large part of the black liquor of the slurry is replaced with the white liquor or the like before, slurring and the replaced black liquor is separated and recovered, or discarded to obtain the objective pulp by using a continuous cooking tank 32.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method and apparatus for continuously cooking cellulose fibrous materials.

[Prior Art and Problems] Efforts have been continuously made to improve the quality of chemical pulp produced in the technology of producing paper pulp from pulverized cellulose fiber materials, such as wood chips, using a digester. . For example, US patent application Ser. No. 07/200.204, filed May 31, 1988, discloses a method and apparatus for improving the quality of pulp.

The method and apparatus of this patent application improve pulp quality by minimizing mechanical effects on the chips, especially when high temperature and pressure conditions are present or when chemical agents are present. It is due to this. This patent application also teaches a method for making the process more uniform.

An object of the present invention is to further improve the quality of chemical pulp produced.

[Means for Solving the Problems] According to the present invention, the quality of chemical pulp (particularly its shear strength and desired beating characteristics) is improved by a simple method. In conventional systems, the extracted black liquor is sent to a series of flash tanks for concentration and then to an evaporator for the final recovery of the chemicals therein. According to the invention, the black liquor from the out-of-stock flash tank is removed by a separate mechanism,
In other words, it is sent to the previous step, where it is crushed cellulose fiber @ (
: Slurry the material with liquid. In this way, materials such as wood chips, for example, remain in contact with dark black liquor for a significant period of time, and the black liquor will partially sulfonate the lignin within the chips. Finally, this slurry is sent to a high pressure feeder and then to a solid/liquid separator.
The black liquor is separated from the black liquor, and the black liquor is sent for final recovery (including the use of a second flash tank), and white liquor is added to it. This is before it is actually fed to the operational part of the continuous digester for chemical digestion at higher sulfidities.

According to the present invention, there is provided a method for continuously cooking pulverized cellulose fiber material with a high degree of sulfidation to produce paper pulp using a continuous digester. The method includes the following steps. (a) steaming of the pulverized cellulose fibrous material; (b) slurrying the material by waves; (c) feeding the slurry of the steamed material to the digester; (d) using white liquor. (e) extracting black liquor from the digester; (f) circulating the black liquor through the steamed pulverized cellulose fibrous material of step (b) to form a slurry; (g) replacing most of the black liquor of the slurry with white liquor or the like prior to step (d) and separating the replaced black liquor; and (h) separating the black liquor from the slurry. The process of sending the liquid to a recovery process or disposal process.

Preferably, step (f) is carried out by transferring the black liquor to a first flash tank to obtain steam and concentrated black liquor, and step (a) is carried out in part by transferring the steam from the first flash tank to a first flash tank. It is done by using

According to another embodiment of the invention, an apparatus is provided for continuously digesting cellulosic fibrous material to produce chemical pulp. The present invention includes the following components. (a) steaming means for steaming fibrous materials; (
b) a liquid slurrying means for producing a slurry liquid containing the steamed four ingredients; (c) a high-pressure feeder having a low-pressure inlet, a low-pressure outlet, a high-pressure inlet, and a high-pressure outlet;
d) a continuous digester; (e) black liquor withdrawal means for withdrawing black liquor from said continuous digester; (f) a first flash tank comprising a steam and concentrate outlet; (g) a first flash tank containing a steam and concentrate outlet; coupling means interconnecting the concentrate outlet with the slurrying means; (h) blackill recovery or dumping means; and (i) means operably coupling the low pressure outlet of the high pressure feeder to the recovery or dumping means.

The installation of the high pressure feeder and solid/branch separator will depend on the particular digester used.

US Patent No. 07/20 filed May 31, 1988
No. 0,204, or as filed on June 28, 1989, "Low cost, low horsepower consumption, and low pulp quality deterioration.
A digester, such as that shown in US patent application Ser. No. 07/372,650, entitled Apparatus and Method for Continuous Cooking of Cellulosic Fiber Materials, or a conventional continuous digester can be used. Slurrying of the material can be carried out in a chute located downstream of a horizontal steaming tank or in an upright tank having a steaming section at the top and a skin surface inside.

The main object of the present invention is to provide a method and apparatus for producing chemical pulp of improved quality as a result of increased sulfidity using a continuous digester.

This and other objects of the invention will become apparent from a study of the detailed description of the invention and the claims.

Now, the present invention will be explained in detail with reference to the drawings. 1st
Most of the components of the apparatus shown in Figures 3 to 3 are conventional in continuous digesters.

For example, a chip storage tank 10 (preferably a vibrating type)
is equipped with an air tank 11 at its top, and a connection port 1 for performing atmospheric pressure tank steaming with flash steam from flash tanks 25 and 26.
2 is attached, and further below it is a chip weigher 1.
3, and a low pressure feeder 14' leading to a horizontal low pressure steaming tank 15'. Next, the chips are playing cards (tr
amp) material separator to a chip chute 15 connected to a high pressure feeder 16 where it is slurried with liquid. These components include an in-line drain 17, a level tank 18, a sand separator 19,
and other components such as each scale pipe, such as pump 2
0.21, 22 and 23, etc., and is also connected to a conduit 24, to which white liquor is added.

The drain 17 communicates with the chute 15 via a conduit 17'. Other conventional components include flash tanks 25 and 26; heater 27 supplied with high pressure steam; white liquor inlet pipe 28; wash heater 29 supplied with high pressure steam; and pump 30.

In the embodiment of FIG. 1, the continuous digester 32 is not a conventional digester, but rather a
It is as described in the specification of No. 650. It includes a concentric double riser tube 34 that is connected to an in-line solid/liquid separator 36 near the top of the digester 32, which tube is equipped with an internal screw 37 and an annular screen 38. The screw 37 is driven by three motors.

The chips then travel upwards past the screw 37 into the top of the digester 32 where they are heated by high pressure steam and then flow down the outside of the conduit 34.

The separated liquid is in the digester 32 but not in the rising conduit 3.
4 to a flow line 42 and ultimately back to the high pressure pump 23 of the feeder 16. Digester 3
Screen 44 near the top of 2 then pumps 46
, a high-pressure steamer 47, and a line 45 extending to a return conduit 48, the separated liquor, once the white water has been added via conduit 49, is returned to the top of the digester 32, where the chips are Immediately after removal from conduit 34, contact is made therewith. The liquid withdrawn from screen 51 is black liquor, which flows through line 52 to flash tank 25.

Liquid is withdrawn from the screen 53 using a pump 27' and returned via a line 54 to an internal upright conduit 55 having an opening 56 near the screen 53. The returned liquid is introduced through this conduit into the tip after the white peel has been added at conduit 28. From the bottom screen 58, cleaning fluid is introduced near the bottom via a cleaning pump and two heaters. The pulp is finally sent to the digester 32
It is extracted from the outlet 61 at the bottom of the tube.

In Figure 1, black liquor is handled in a conventional manner. The concentrate in line 68 from flash tank 25 goes to second flash tank 26 and the steam in line 64 (through line 65 to junction 12) is used in chip storage tank 10 and/or low pressure steaming. into line 66 leading to tank 15'. In flash tank 26, the vapor is separated in line 69 and the doubly concentrated liquid in line 70 is sent to an evaporator for final chemical recovery.

In FIG. 2, another exemplary apparatus according to the invention is shown. Components in FIG. 2 that correspond to components shown in FIG. 1 are designated by the same reference numerals, only preceded by a "1". Common components do not require further detailed explanation. Only the differences between the system of FIG. 2 and the system of FIG. 1, namely the apparatus for handling black l&, will be described in detail.

In the configuration shown in FIG. 2, the concentrated black liquor from the first flash tank 125 is passed through line 75 to the chip chute 115 where it is used at least in part to slurry the steamed chips. It accounts for the majority. The black liquor is kept in intimate contact with the chips for a considerable period of time. During the contact of the black liquor with the chip,
The lignin in the chips is partially sulfonated by black liquor. Finally, the black liquor is separated and then white liquor etc. are added. This primarily takes place in the impregnation tube 34 between the high pressure feeder 116 and the solid/liquid separator 136.

The low pressure outlet from high pressure feeder 116 is connected to pump 122, which contains a large amount of black liquor. This is because most of the slurrying liquid introduced into the low pressure inlet (chip chute) of high pressure feeder 116 is replaced by the high pressure liquid in line 142. From the in-line drain 117, the black liquor flows in line 77 to a second flush tank 126 and then to a conventional recovery or disposal process. If desired, bypass conduit 7
8 may be provided so that a portion of the concentrated black liquor can flow directly from the first flash tank 125 to the second flash tank 126, and operations to increase the sulfidity are not desirable in the case of In some cases, all of the black liquor may be forced to flow into the tank 126. Then,
By means of a corresponding bypass 79, the high pressure feeder 116
(bypass 79 opens when bypass 78 closes). Line 131 and riser pipe 1
Most of the black liquor remaining in solid/liquid separator 136
and flows through return separation conduit 141 to high pressure supply line 142 and into high pressure pump 123. Of course, the black liquor is eventually replaced with white liquor or the like before the chips are actually cooked in the digester 132.

The pulp produced using the system shown in FIG. 2 has high quality, especially high shear strength, and excellent beating properties.

In the embodiment of FIG. 3, elements corresponding to those shown in FIG. Equivalents to those shown are designated by the same reference numerals, only preceded by a "2".

In FIG. 3, a conventional digester 232 is shown, where slurrying and steaming is carried out using the low pressure steaming tank 115' and chip chute 1 of the embodiment of FIG.
15, but in an upright tank 79. This upright tank 7
At 9, low-pressure steam is introduced at the top to maintain a liquid level of the slurry liquid inside, and the feed liquid is
There is at least a portion of black liquor lightening line 275 from flash tank 125. The slurry flows out from the bottom of tank 79 into supply conduit 80 and into high pressure feeder 216.
to the low-pressure side inlet.

In the embodiment of FIG. 3, a solid/liquid separator is provided, but only as an external structure 81 of the digester 232. Chips containing partially sulfonated lignin flow via line 231 to separator 81, slurry chips flow bidirectionally through conduit 82 to top 83 of digester 232, while separated liquor is Flows to line 242. A portion of the wave in line 242 is fed to high pressure pump 223 of high pressure feeder 216, while the remainder ultimately flows to black liquor line 277 via second flush tank 226.

White liquor is added at many points in the system of FIG. This wave is not added to line 224, but line 8
5 is added to the top of the digester 232 and comes into contact with the chips as soon as they are introduced. The pump 86 is connected to a heater 87, into which white liquor is also introduced, and this white liquor replaces the extracted black liquor in the separator 81. The pump 88 is
Liquid is drawn off through eight screens near the top of tank 232 and sent via line 90 to heater 87 and separator 81.

In the embodiment of FIG. 3, volatile materials, such as terpene oil, exiting in line 95 from chip storage tank 210 and steaming/slurry tank 215 are routed to suitable recovery equipment.

Therefore, it is clear that the present invention provides a convenient method and apparatus for improving the quality of chemical pulp produced in a continuous digester.

The present invention is considered to be the most practical at present, and its preferred embodiments are shown herein,
Having thus been described, it will be apparent to those skilled in the art that many modifications may be made within the scope of the claims. It is therefore intended that the scope of the invention be determined by the broadest interpretation of the appended claims to include all such equivalent methods and apparatus.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an apparatus for feeding fibrous material with conventional black liquor recovery to a continuous digester of the new design. FIG. 2 is a schematic diagram of an apparatus similar to FIG. 1 illustrating black liquor processing according to the present invention. FIG. 3 is a schematic representation of a continuous digester with feed means modified from that of FIG. 2; 10...Chip storage tank, 11...Air tank, 12.
...Connection port, 13...Chip measurer, 14...Playing material separator, 14'...Low pressure feeder, 15,1
15...Chute, 15'...Horizontal low pressure steaming tank, 16.161,216...High pressure feeder,
17... In-line drain device, 18... Liquid level tank, 19... Sand separator, 20. 21.22.23.
86°88.122,123,223...Pump, 2
4゜82...conduit, 25.26,125,126,2
25.226...Flash tank, 27.87...
・Heater, 28...White liquid introduction pipe, 29...Cleaning wave heater, 27', 30.46...Pump, 3
2゜232... Continuous digestion tank, 34... Concentric upward flow conduit (impregnated pipe), 36, 81, 136... Solid/liquid separator, 37... Screw, 38... Circular ring Formula screen, 39...Motor, 41,141.82...
Conduit, 42.45.54.60.64.65,66°6
8, 70. 75. 77.85.90.95°14
2.224,242,275.277... line, 4
4.51, 53.89...Screen, 47...High pressure steamer-148...Return conduit, 4...Conduit,
55... Internal mounting conduit, 56... Closing part, 58...
・Bottom screen, 61...Exit, 78.79...
Bypass conduit, 80...Feeder conduit, 83...
Top, 215... Upright tank, 74... Upright tank, 75.
...Liquid level, 76...Bottom scraper

Claims (10)

[Claims] (1) A method of continuously cooking pulverized cellulose fiber material by increasing the degree of sulfidation to produce paper pulp using a continuous digester (32), comprising: (a) a step of steaming the pulverized cellulose fiber material; (b) slurrying the material with a liquid; (c) supplying the slurry liquid of the steamed material to the digester; (d) kraft cooking of the material in the digester using white liquor; and (e) in a process for continuous cooking of high sulfidity paper pulp comprising the step of withdrawing black liquor from the digester, the following steps are carried out, namely: (g) replacing a majority of the black liquor of the slurry with white liquor or the like prior to step (d) and separating the displaced black liquor; and (h) a continuous cooking method for high sulfidity pulverized cellulose fiber material, characterized by the step of sending the separated black liquor to a recovery step or a disposal step. (2) Step (f) is to transfer the black liquor to the first flash tank (2
5) to produce steam and more concentrated black liquor.
1) The method described. 3. The method of claim 1, further characterized in that step (a) is carried out at least in part by using steam from the first flash tank (25). (4) Step (g) also involves transferring the slurry to a solid/liquid separator (3
6) The method according to claim 1, further characterized in that the method is further carried out by sending to 6). (5) Step (g) is to transfer the slurry to a high pressure feeder (16
) and then to a solid/liquid separator (36).
Method described. (6) Apparatus for continuously digesting pulverized cellulose fibrous material for the production of paper pulp, comprising: (a) steaming means (110, 1) for steaming said material;
15'), (b) liquid slurrying means (115) for producing a slurry liquid containing the steamed material, (c
) a high pressure feeder (46) having a low pressure inlet, a low pressure outlet, a high pressure inlet, and a high pressure outlet; (d) a continuous digester (132);
), (e) black liquor extraction means (151, 152) for extracting black liquor from the continuous digester, (f) steam (
64) and a concentrate (168) outlet; and (g) a black liquor recovery or dumping means (170). (h) means (7) interconnecting said concentrate outlet from said flash tank with said slurrying means;
5), and means (122) for connecting the low pressure outlet of the high pressure feeder to the recovery or dumping means. (7) The steaming means and the slurrying means include a vertically disposed tank (215), which maintains a liquid level therein, and above the liquid level, a steam inlet means, and 7. The method of claim 6, further comprising a slurry outlet (180) at the bottom of the vessel, which slurry outlet is connected to a low pressure inlet of the high pressure feeder. (8) Further characterized in that said slurrying means comprises a vertically disposed chute (115) and said steaming means is a generally horizontal steaming tank (115'). ) method described. (9) a line (42, 1) operably interconnected between the high pressure feeder and the continuous digester;
7. The method of claim 6, further comprising a solid/liquid separator (36, 136) interconnected with the high pressure outlet from the high pressure feeder by 42). (10) The continuous digester has a slurry inlet (31) located at its bottom, a central rising conduit (34) extending upward from the slurry inlet, and a central rising conduit (34) above the rising conduit.
6) a solid/liquid separator located near the top of the digester and rising within the digester for separating liquid from the digester and feeding this liquid to the high pressure inlet to the high pressure feeder; 7. The method of claim 6, further comprising including a separating liquid conduit (42) outside the flow conduit extending downwardly towards the bottom of the digester.